Electrochemical Characterization of Self‐Assembled Thiol‐Porphyrin Monolayers on Gold Electrodes by SECM

Abstract

Herein, the scanning electrochemical microscopy (SECM) approach is applied to study the formation of thiol-porphyrin self-assembled monolayer (SAMs). Using cyclic voltammetry (CV), the formation process is characterized adopting different probe molecules. The observed phenomena indicate that the formation process is affected by solution properties and the molecular structure of the probe molecules. In K(3)Fe(CN)(6) , the SAMs show a strong electron-transfer (ET) blocking effect on a pure porphyrin-modified electrode. However, addition of metal ions to the porphyrin molecules leads to ET. A consistent tendency is observed throughout the modification process using CV and SECM methods. Furthermore, k(eff) values, the apparent heterogeneous rate constants, obtained for different modification periods affirm the validity of these results. SECM images are used to collect surface information in the course of the modification process when the substrate potential is 0.5 V versus Ag/AgCl. The effect of the substrate potential indicates that the oxidation of the porphyrin molecules is supported by more positive potentials because of the similar bimolecular reaction of the porphyrin ring with positive charge and the probe molecules with negative charge.

Self Assembled Films of Porphyrins with Amine Groups at Different Positions: Influence of Their Orientation on the Corrosion Inhibition and the Electrocatalytic Activity

“…After modifying the gold electrode with either Co(II)(T(o-NH 2 )PP) or Co(II)(T(p-NH 2 )PP), the cyclic voltammogram no longer shows any redox peaks (curves b and c). Their suppression is consistent with the presence of a film layer or coating on the gold electrodes [ 47 ].…”

Cathodic electrochemiluminescence of meso-tetra(4-carboxyphenyl) porphyrin/potassium peroxydisulfate system in aqueous media

“…Many researchers have paid close attention to porphyrins due to their special photoelectric properties [27][28][29]. But the investigation about ECL of porphyrin is very limited.…”

Study of the adsorption kinetics of thiol-derivatized porphyrin on the surface of gold electrode

“…We have recently studied on the distance dependence of heterogeneous electron transfer kinetics of self-assembled monolayers formed by a series of thiol-functionalized porphyrin derivatives with different alkyl chain length [20][21][22]. The adsorption molecules, such as 5-[p-(mercaptopropyloxy)-phenyl]-10,15,20-triphenylporphyrin, 5-[p-(mercaptobutoxy)-phenyl]-10,15,20-triphenylporphyrin, 5-[p-(mercaptohexoxy)-phenyl]-10,15,20-triphenylporphyrin, 5-[p-(mercaptononoxy)-phenyl]-10,15,20-triphenylporphyrin, 5-[p-(mercaptodecoxy)-phenyl]-10,15,20-triphenylporphyrin and 5-[p-(mercaptododecoxy)-phenyl]-10,15,20-triphenyl-porphyrin (abbreviated as H 2 TPPO(CH 2 ) n SH, where n = 3, 4, 6, 9, 10 and 12) contain an electroactive center as a large terminal group with variable alkyl chain length.…”